Inhibition of polymerization of monomeric compounds containing vinyl groups



Patented Sept. 26, 196? 3,344,144 INHIBITION OF POLYMERIZATION OF MONO- MERIC COMPOUNDS CONTAINING VINYL GROUPS Tadahiro Kohayashi, Fuji-shi, Japan, assignor to Asahi Kasei Kogyo Kahushiki Kaisha, Osaka, Japan, a corporation of Japan No Drawing. Original application June 13, 1963, Ser. No. 287,516, now Patent No. 3,274,231, dated Sept. 20, 1966. Divided and this application July 21, 1965, Ser. No. 482,657

2 Claims. (Cl. 260-290) ABSTRACT OF THE DISCLOSURE A method for stabilizing an unsaturated vinylic compound by adding to vinyl acetate, vinyl propionate, vinyl chloride, vinylidene chloride, vinyl sulfonic acid, methallyl sulfonic acid, p-styrene sulfonic acid, 2-methyl-5-vinyl pyridine, 4-vinyl pyridine or N,N-dimethylaminoethyl methacrylate, 0.5 to 2,000 ppm. of at least one stabilizer selected from the group consisting of acetonethiosemicarbazone, acetophenonethiosemicarbazone, acetoaldehydethiosemicarbazone, acetylthiosemicarbazide, phenylthiosemicarbazide, formylthiosemicarbazide, carbaminylthiosemicarbazide, thiosemicarbazide, iononethiosemicarbazone, acetonesemicarbazone, acetoaldehydesemicarbazone, acetophenonesemicarbazone, acetylsemicarbazide, phenylsemicarbazide, iononesemicarbazone, and semicarbazide to produce a stabilized composition consisting of said unsaturated com-pound and said stabilizer. The thusly stabilized unsaturated compound, when polymerized, produces a colorless polymer possessing thermal stability even with the stabilizer present therein.

This application is a divisional of my previously filed application Serial No. 287,516 filed June 13, 1963 which has matured as U.S. Patent No. 3,274,231.

This invention relates to a method for inhibiting the polymerization of polymerizable unsaturated organic monomers.

It is well known that polymerizable unsaturated organic monomers are denatured when they are transferred or stored at room temperatures or subjected to elevated temperatures, such as encountered during distillation of monomers.

It is also well known that stabilizers are added to the monomers in order to avoid such denaturation. However, it has also been experienced that polymers are colored when the polymer is made from the monomers containing stabilizers, t-butylcatechol, hydroquinon and p-methoxyphenol, for example, which are familiar stabilizers for acrylonitrile, acrylates or methacrylates reduce whiteness or the thermal stability in whiteness of polymers thereof, and sometimes they inhibit polymerization to adversely effect the polymerization yield and molecular weight distribution, even if they are contained in the monomers in a minor amount. Accordingly, the monomers should be thoroughly purified before they are polymerized, with the result that they require severe distillation and consequent loss of monomer.

It is an object of the present invention to provide new stabilizing agents for polymerizable unsaturated organic monomers which avoid denaturation of the monomers and do not color polymers obtained therefrom.

It is an other object of the present invention to provide new stabilizing agents for polymerizable unsaturated organic monomers which give polymers superior thermal stability in whiteness, even if the stabilizers remain there- It is a further object of the present invention to pro vide a method for stabilizing polymerizable unsaturated organic monomeric compounds.

According to the present invention, compounds represented by the general formula of wherein X represents a sulphur or oxygen atom are admixed with polymerizable unsaturated, organic compounds.

The polymerizable, unsaturated organic compounds according to this invention are vinyl esters, e.g., vinyl acetate, vinyl propionate, etc., vinyl and vinylidene halides, e.g., vinyl chloride vinylidene chloride, etc; vinyl compounds containing suifonic acid groups, e.g., vinyl sulfonic acid, methallyl sulfonic acid, p-styrene sulfonic acid, etc.; vinyl compounds containing basic nitrogen atom, e.g., 2-methyl-5-vinyl pyridine, 4-vinyl pyridine and N,N-diethylaminoethylmethacrylate. The following compounds are also stabilized by the substances according to the invention but are the subject of my parent application and other divisional applications Serial Nos. 482,658, and 482,659: acrylonitrile and alkyl substituted compounds thereof, e.g., methacrylonitrile, dimethyl acrylonitrile, etc.; acrylic acid and its alkyl substituted compounds thereof, e.g., methacrylic acid, ethacrylic acid, etc.; and alkyl esters of such acids, e.g., methyl methacrylate, ethylmethacrylate, butylmethacrylate, methylacrylate, ethyl acrylate, propyl acrylate, butyl acrylate, etc. and amides of such acids, e.g., acrylamide, methacrylamide, etc.; styrene and alkyl substituted compounds thereof, e.g., p-methylstyrene, etc.

The compounds to be added include acetonethiosemicarbazone, acetaldeydethiosemicarbazone, acetophenonethiosemicarbazone, acetylthiosemicarbazide, phenylthiosemicarbazide, formylthiosemicarbazide, carbaminylthiosemicarbazide, thiosemicarbazide, acetonesernicarbazone, acetaldehydesemicarbazone, acetophenonesemicarbazone, acetylsemicarbazide, semicarbazide, phenylsemicarbazide and iononesemicarbazone.

The stabilizer compounds may be used in an amount of 0.5 to 2,000 p.p.m., preferably 1-50 p.p.m.

These stabilizers produce no adverse effects when monomers having the stabilizers are subjected to polymer ization in the presence of peroxide or redox type catalysts.

Example 1 In order to show the eifectiveness of the present inhibitors in comparison with other known inhibitors a test was carried out in which acrylonitrile containing the 3 inhibitors to be compared was subjected to the oxygen bomb test, which is conventionally employed for determining the stability of gasoline in the presence of oxygen at high pressures. This test was carried out as follows:

42' tion to the above accelerated stability test carried out in the presence of oxygen at elevated temperatures and high pressures, it has been found that the present inhibitors are efiective in prolonged storage under normal atmos- Using a graduated cylinder, 25 ml. of acrylonitrile 5 pheric conditions. containing the inhibitor was introduced into the glass Acrylic fibre was prepared by polymerizing acryloliner. The liner was placed in the stainless steel bomb, nitrile (containing the inhibitor), without removing the connected to a pressure recording gauge and the bomb inhibitor, dissolving in 55-80% nitric acid. The thermal was closed tightly. Oxygen was added to a pressure of 100 stability in whiteness of the acrylic fibres thus prepared pounds per square inch gauge at room temperature. The were very good and showed negligible color formation. bomb was placed in a steam bath and the pressure char- E l 2 acteristics were noted over a four-hour period. xamp e As the bomb becomes heated, the pressure rises gradu- In order to show the effeetivehess f the present any to {lbout 9 PoundS Per Square Inch gauge- If the inhibitors in comparison with other known inhibitor a sample 15 Potentlany mIStabIQ the Pressure after level 15 test was carried out in which acrylic esters, such as li ig lol f, will drop, then ncrease rapidly, and the acrylomethylaerylste ethyl ael-ylate and hutyl acrylate, and will become Q Sohd q If Q sudden presslfre methacrylic esters such as methylmethacrylate containing drop noted and lfflo 9 Y formed dUmPg the inhibitors to be compared was subjected to a viscosity the four-hour test period, the inhibitor is considered satistest Whieh was carried out as follows; factory- 1' In a 100 cc. Erlenmeyer flask, an inhibitor and 0.025 The abqve to aclylommle contalmng grams of 2,2-azobisisobutylonitrile is dissolved in 60 the following inhibitors. Tertiary butyl catechol, hydrograms of aeryhe ester or methacrylic esteh This fl k quinoiie monomethyl ether, thiosemicarbazide, acetaldeis placed in a thermostat maintained at Q The hydethiosemicarbazone, acetonethiosemicarbazone, aceviscosity of 5 Ce samples taken at fixed intervals f tophenonethiosemicarbazone, semicarbazide, acetonesemithe hash is measured by an Ostwald viseosimeter When c arbazone, acetaldehydesemicarbazone. The table men-. the viscosity fails to rise abruptly Within 6 hours, the tioned hereinunder shows the concentrations as well as inhibitor is considered effective the efiect upon the acrylomtnle- The above test was applied to methyl acrylate, ethyl ISO O ORS acrylate, butyl acrylate and methylmethacrylate containing the following inhibitors: 1 rllemary Putyl catechol Hydroquinone monomethyl ether I-iydroquinone monomethyl ether 10 2 iosemicarbazide Hydroquinone monomethyl ether 2O Acetonethiosemicarbazone Thlosemlcarbazlde 25 Ac t lthiosemicarbazide Acetaldehydethiosemicarbazone 2 4 segfiiarbaide Acetonethiosemicarbazone 4 A t b Acetophenonethiosemicarbazone 4 Ce oneserfucar afone Semicarhazide 2 8 phenylsemlcarbflllde Aeetohesemiearhazohe 2 8 4O Acetaldehydethiosemicarbazone Acetaldghydesemlcarbazone 2 8 The table hereinunder mentioned shows the concen- 1 Sample polymerized. trations as well as the effect upon the acrylic esters and 2 No polymer formed. methacrylic esters.

COMPARISON OF INHIBITORS Concentration Inhibited Monomers Inhibitors of inhibitors period (p.p.ni.) (hour) Methyl acrylate -e Hydroquinone monomethyl 2 300 OverG 30 Do. 25 D0. 30 D0. Acctylthioscmicarbazide. 35 Do. Thioscinicarbazide 30 Do. Semicai'bazide 40 D0. Acetonesemicarbazonm 40 D o. Phcnylsemicarbazide 40 D0. Acetaldeliydethiosernicarbazonm 40 D0.

The above data show that the inhibitors according to the present invention are effective at lower concentrations than the conventional inhibitors of the prior art. In addition to this superiority in that a smaller amount of the inhibitors is necessary, the present inhibitors have the The above data show that the present inhibitors are effective at lower concentrations than the conventional inhibitors of the prior art. In addition to this superiority in that a smaller amount of the inhibitors is necessary, the present inhibitors have the further advantages of negligifurther advantages of negligible color formation. In addible color formation. In addition to the above accelerated stability test carried out, it has been found that the present inhibitors are effective in prolonged storage under normal atmospheric conditions.

semicarbazone, acetonesemicarbazone, acetoaldehydesemicarbazone, acetophenonesemicarbazone, acetylsemicarbazide, phenylsemicarbazide, iononesemicarbazone, and semicarbazide.

Exam le 3 p 5 2. A composition comprising a vinyl compound se- El'fectiveness of the present inhibitors were lnvestigated. lected from the group consisting of vinyl acetate, vinyl Monomers to which the inhibitors were added weighed propionate, vinyl chloride, vinylidene chloride, vinyl sul- 100 g., respectively and were left to stand under atmosfonic acid, methallyl sulfonic acid, p-styrene sulfonic acid, pheric pressure, at room temperature for one year, except Z-methyl-S-vinyl pyridine, 4-vinyl pyridine and N,N-difor vinylchloride in a bomb for one year, to observe 10 methylaminoethyl methacrylate, and 0.5 to 2,000 ppm. changes of viscosity as well as appearance. respectively of at least one stabilizer selected from the TABLE Monomers Inhibitors Cone Viscosity Appearance Acrylonitrile Thiosemicarbazide .t Unchanged Unchanged. Methacrylonitrile Acetonethiosemicarbazone. 30 do D0. Acrylic acid Acetylthiosemicarbazide Do. Methacrylie acid Semicarbazide Do. Ethaerylic acid t. Acetonesemicarbazone. t. Do. Methylmethaerylate. Acetaldehydesemicarbazone D0. Ethylrnethacrylate Acetaldehydethiosernicarbazon Do. Butylrnethaerylate Phenylsemicarbazide Do. Methylacrylate Acetonethiosemicarbazon Do. Ethylacrylate Thiosemiearbazide. Do. Propylacrylate- Acetonesemiearbazon Do. Butylaerylate Acetaldehydesemicarba Do. Styrene Acetonethiosemicarbazone Do. p-Methylstyrene Semicarb azide t Do. Vinylacetate Acetaldeh ie D0. Vinylchloride Acetaldehydesemicarbazone- Do. Vinylidenechloride Semiearbazide. Do. Vinylsulfonic acid... Phenylsemicarbazi Do. Methallylsulfonic acid, Acetonethiosemicarbazo D0. p-StyTene sultonic acid Thiosemicarbazide- Do. 2-methyl-5-vinyl pyridine- 0 D0. 4 vinylpyridine Acetaldehydethiosemlcarbazo Do. N,N-dhnethylaminoethylmethac Semicarbazlde Do.

It will be seen from the above table that lower amount of the present inhibitors than conventional ones is sufficient to stabilize the various polymerizable organic monomers. Furthermore, the present inhibitors do not color the monomers at all.

What I claim is:

1. A method comprising stabilizing a vinyl compound selected from the group consisting of vinyl acetate, vinyl propionate, vinyl chloride, vinylidene chloride, vinyl sulfonic acid, methallyl sulfonic acid, p-styrene sulfonic acid, 2-methyl-5-vinyl pyridine, 4-vinyl pyridine and N,N-dimethylaminoethyl methacrylate, by adding to said compound 0.5 to 2,000 ppm. respectively of at least one stabilizer selected from the group consisting of acetonethiosemicarbazone, acetophenonethiosemicarbazone, acetoaldehydethiosemicarbazone, acetylthiosemicarbazide, phenylthiosemicarljazide, formtylthiosemicarbazide, carbaminylthiosemicarbazide, thiosemicarbazide, iononethio- References Cited Rice: J. Am. Chem. Soc., vol. 45, pp. 222-225 (1923). Delaby et al.: Chem. Abstracts, vol, 46, par. 6616 (1952).

WALTER A. MODANCE, Primary Examiner. A. L. ROTMAN, Assistant Examiner. 

1. A METHOD COMPRISING STABILIZING A VINYL COMPOUND SELECTED FROM THE GROUP CONSISTING OF VINYL ACETATE, VINYL PROPIONATE, VINYL CHLORIDE, VINYLIDENE CHLORIDE, VINYL SULFONIC ACID, METHALLYL SULFONIC ACID, P-STYRENE SULFONIC ACID, 2-METHYL-5-VINYL PYRIDINE, 4-VINYL PYRIDINE AND N,N-DIMETHYLAMINOETHYL METHACRYLATE, BY ADDING TO SAID COMPOUND 0.5 TO 2,000 P.P.M. RESPECTIVELY OF AT LEAST ONE STABILIZER SELECTED FROM THE GROUP CONSISTING OF ACETONETHIOSEMICARBAZONE, ACETOPHENONETHIOSEMICARBAZONE, ACETOALDEHYDETHIOSEMICARBAZONE, ACETYLTHIOSEMICARBAZIDE, PHENYLTHIOSEMICARBAZIDE, FORMYLTHIOSEMICARBAZIDE, CARBAMINYLTHIOSEMICARBAZIDE, THIOSEMICARBAZIDE, INONETHIOSEMICARBAZONE, ACETONESEMICARBAZONE, ACETOALDEHYDESEMICARBAZONE, ACETOPHENONESEMICARBAZONE, ACETYLSEMICARBAZIDE, PHENYLSEMICARBAZIDE, IONONESEMICARBAZONE, AND SEMICARBAZIDE. 